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Accuracy of Unmanned Aerial Vehicle (UAV) and SfM Photogrammetry Survey as a Function of the Number and Location of Ground Control Points Used
摘要： The geometrical accuracy of georeferenced digital surface models (DTM) obtained from images captured by micro-UAVs and processed by using structure from motion (SfM) photogrammetry depends on several factors, including flight design, camera quality, camera calibration, SfM algorithms and georeferencing strategy. This paper focusses on the critical role of the number and location of ground control points (GCP) used during the georeferencing stage. A challenging case study involving an area of 1200+ ha, 100+ GCP and 2500+ photos was used. Three thousand, four hundred and sixty-five different combinations of control points were introduced in the bundle adjustment, whilst the accuracy of the model was evaluated using both control points and independent check points. The analysis demonstrates how much the accuracy improves as the number of GCP points increases, as well as the importance of an even distribution, how much the accuracy is overestimated when it is quantified only using control points rather than independent check points, and how the ground sample distance (GSD) of a project relates to the maximum accuracy that can be achieved.
关键词： Unmanned Aerial Vehicles (UAV),accuracy,structure from motion,ground control points
更新于2025-09-10 09:29:36
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An overview of the methods for deriving recurrence relations for T-matrix calculation
摘要： In this paper, we present a consistent analysis of the methods dealing with the derivation of recurrence relations for calculation of the T -matrix. Central and forward recurrence relations are obtained in the framework of the invariant embedding T -matrix method, the matrix Riccati equation method, and the superposition T -matrix method. The accuracies and e?ciencies of the central and forward recurrence schemes are analyzed, and some implementation issues related to the improvement of the numerical accuracy and to the problem of overcoming of over?ow errors are discussed.
关键词： recurrence relations,matrix Riccati equation,over?ow errors,invariant embedding,superposition T-matrix method,numerical accuracy,T-matrix
更新于2025-09-10 09:29:36
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Pursuing High Quality Phase-Only Liquid Crystal on Silicon (LCoS) Devices
摘要： Fine pixel size and high-resolution liquid crystal on silicon (LCoS) backplanes have been developed by various companies and research groups since 1973. The development of LCoS is not only bene?cial for full high de?nition displays but also to spatial light modulation. The high-quality and well-calibrated panels can project computer generated hologram (CGH) designs faithfully for phase-only holography, which can be widely utilized in 2D/3D holographic video projectors and components for optical telecommunications. As a result, we start by summarizing the current status of high-resolution panels, followed by addressing issues related to the driving frequency (i.e., liquid crystal response time and hardware interface). LCoS panel qualities were evaluated based on the following four characteristics: phase linearity control, phase precision, phase stability, and phase accuracy.
关键词： spatial light modulator,phase accuracy,spatially anamorphic phenomenon,liquid-crystal-on-silicon,phase precision and stability,holographic display
更新于2025-09-10 09:29:36
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Evaluation of linear measurements of implant sites based on head orientation during acquisition: An ex vivo study using cone-beam computed tomography
摘要： Purpose: This study evaluated the effect of various head orientations during cone-beam computed tomography (CBCT) image acquisition on linear measurements of potential implant sites. Materials and Methods: Six dry human skulls with a total of 28 implant sites were evaluated for seven different head orientations. The scans were acquired using a Hitachi CB-MercuRay CBCT machine. The scanned volumes were reconstructed. Horizontal and vertical measurements were made and were compared to measurements made after simulating the head position to corrected head angulations. Data was analyzed using a two-way ANOVA test. results: Statistical analysis revealed a significant interaction between the mean errors in vertical measurements with a marked difference observed at the extension head position (P<0.05). Statistical analysis failed to yield any significant interaction between the mean errors in horizontal measurements at various head positions. conclusion: Head orientation could significantly affect the vertical measurements in CBCT scans. The main head position influencing the measurements is extension. (Imaging Sci Dent 2015; 45: 73-80)
关键词： Dental Implants,Dimensional Measurement Accuracy,Patient Positioning,Cone-Beam Computed Tomography
更新于2025-09-10 09:29:36
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[IEEE 2018 2nd International Conference on Engineering Innovation (ICEI) - Bangkok (2018.7.5-2018.7.6)] 2018 2nd International Conference on Engineering Innovation (ICEI) - Diabetic retinopathy fundus image classification using discrete wavelet transform
摘要： Diabetes is an incurable disease which erodes away body slowly, this disease in becoming common and becoming a cause of social distress. The only solution to this problem is early detection of disease and take precautionary measure to keep its effects to minimum. Since it affects various parts of body, the affected organ also includes eye which is very sensitive to any kind of distress. Diabetic Retinopathy effects of diabetes on eye retina, which includes rupturing of retina blood vessels and abnormal growth of blood vessels in retina, which ultimately causes blindness. Diabetic Retinopathy can be identified by examining the retinoscopy images. In this paper, retinoscopy images were processed using wavelet transform. Wavelet coefficients extracted from the images were obtained to identify Diabetic Retinopathy. KNN and SVM were used to classify the retinoscopy images. This papers have shown remarkable improvement as compared to previous studies, with KNN at 98.16 % accuracy and SVM at 97.85 % accuracy.
关键词： sensitivity,specificity,Discrete Wavelet Transform (DWT),accuracy,KNN,Diabetic Retinopathy (DR),histogram equalization,SVM
更新于2025-09-10 09:29:36
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Design considerations of a surface plasmon resonance (SPR) based tapered fiber optic bio-sensing probe with graphene-MoS2 over layers
摘要： In this paper, we have reported the design considerations of a surface plasmon resonance (SPR) based tapered fiber optic sensor by coating a thin film of platinum on a tapered fiber core followed by graphene-molybdenum disulphide (MoS2) monolayers. The theoretical study is based on five-layer matrix model. To see the effect of graphene-MoS2 over layers, performance parameters in terms of sensitivity and detection accuracy are evaluated for four taper profiles viz. exponential-linear, linear, parabolic and quadratic along with the taper ratio. From results, we inferred that with increase in taper ratio sensitivity also increases while detection accuracy decreases monotonically. For the proposed sensor configuration, maximum sensitivity value is found to be 7.04μm/RIU at taper ratio 2.0 for exponential-linear taper profile while maximum detection accuracy obtained is 16.7623μm-1, at taper ratio 1.0. Thus, the results show that by introducing additional graphene-MoS2 monolayers, the sensitivity of the proposed sensing probe is enhanced by more than 44% at taper ratio 2 as compared to the conventionally used SPR based fiber optic sensors coated with platinum only. Also, the effect of increasing number of layers of graphene and MoS2 on the performance parameters is evaluated and compared. The advantageous features of the graphene and MoS2 layers have also been discussed for bio-sensing applications.
关键词： surface plasmon resonance,graphene,Fiber optic sensors,sensitivity and detection accuracy,molybdenum di-sulphide
更新于2025-09-09 09:28:46
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[American Society of Agricultural and Biological Engineers 2018 Detroit, Michigan July 29 - August 1, 2018 - ()] 2018 Detroit, Michigan July 29 - August 1, 2018 - <i>The Assessment of Accuracy and Stability for a UAS Sensor Platform as a Precision Agriculture Management Tool in Detecting and Mapping Geospatial Field Variability</i>
摘要： The unmanned aerial system (UAS), that is used as a precision agricultural management tool for detecting and mapping geospatial variability in the crop health of the agricultural row field, is dependent on global positioning system (GPS) receivers and remote sensor (RS) systems. Unlike a ground platform, the UAS is subject to additional platform factors such as autonomous flight system, inertial navigational system (INS), aerodynamics, and aerial climate conditions which can affect flight path accuracy and stability. Such factors can result in diminished quality of trajectory accuracy or aerial Nadir stability that is needed for the precision mapping of geospatial variability zones that are used in the management decisions for geospatial input of treatments. The diminished quality of the UAS flight path can in turn cause RS image-stitching distortions that will render a precision treatment zone map geospatially insufficient. Using the scientific method, this project proposes bringing geospatial assessment tools to the agricultural field that serve to independently verify the flight path accuracy and stability aspects of any UAS sensor platform apart from sole reliance on ortho-stitching processing or sole reliance on on-board platform systems. In a field, a set pattern of elevation posts with global navigational satellite system (GNSS) obtained coordinates will be erected to be viewed from the Nadir orientation of any UAS. With any UAS autonomous platform equipped for optically tracking geospatial flight path metrics, the UAS flight path will follow the posted field pattern at various altitudes. The expected result will be a repeatable testing regimen that will be suitable in standardizing the assessment of any UAS sensor platform for flight path stability and accuracy where precision mapping and true global accuracy are needed such as in the management decisions for the geospatial input of treatments.
关键词： sensor platform,timeliness,unmanned aerial system (UAS),Accuracy,Nadir view stability,testing regimen,geospatial variability (GSV),site specific management (SSM)
更新于2025-09-09 09:28:46
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[IEEE 2018 34th International Conference on Lightning Protection (ICLP) - Rzeszow (2018.9.2-2018.9.7)] 2018 34th International Conference on Lightning Protection (ICLP) - Optical Lightning Measurement System and First Results
摘要： This paper introduces a newly developed optical lightning measurement system (OLMS). The OLMS is based on a video system using a camera with a 360° panorama view and a frame rate of 60 frames per second. The OLMS locates the lightning from the direction of the illuminated lightning channel and the travel time of the thunder sound. The analysis comprises 34 flashes containing 144 strokes, which occurred during the time period from 30th of July 2017 to 24th of August 2017. The results are compared to data obtained by the European lightning location network EUCLID. The comparison revealed a flash detection efficiency of 100 % and a stroke detection efficiency of 93.1 % for EUCLID. With EUCLID, the fraction of 92.5 % was classified correctly as cloud-to-ground lightning and the minor fraction of 7.5 % was miss-classified as cloud-to-cloud lightning. On average (arithmetic mean), the negative flashes contained 4.3 return strokes with 1.7 different striking points. For multi-stroke flashes with return strokes using the same lightning channel, EUCLID located the individual striking points with a median deviation of 57.3 m. The average striking distance was about 10 km. Due to the far distance the thunder sound could often not be separated from the thunder sound of other lightning. Therefore, the OLMS located the lightning with a relatively high deviation compared to the data of EUCLID. The arithmetic (geometric) mean value of the deviation was 1330 m (670 m).
关键词： optical measurement,detection efficiency,Lightning location system (LLS),multiple lightning flash,location accuracy,selectivity CG/CC
更新于2025-09-09 09:28:46
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Peripapillary microvasculature in the retinal nerve fiber layer in glaucoma by optical coherence tomography angiography: focal structural and functional correlations and diagnostic performance
摘要： To quantify peripapillary microvasculature within the retinal nerve fiber layer (RNFL) in primary open-angle glaucoma (POAG) and normal eyes, determine association of perfusion parameters with structural and functional measures, and report diagnostic accuracy of perfusion parameters. Patients and methods: POAG and normal patients underwent 6×6 mm2 optic nerve head scans (Angioplex optical coherence tomography angiography [OCTA]; Cirrus HD-OCT 5000) and Humphrey Field Analyzer II-i 24-2 visual field (VF) testing. Prototype software performed semiautomatic segmentation to create RNFL en face images and quantified vessel area density (VAD), vessel skeleton density (VSD), and vessel complexity index (VCI) in the optic nerve head globally and focally. Generalized estimating equations models assessed association of OCTA parameters with VF mean deviation (MD) and RNFL thickness. Results: Thirty-eight POAG and 17 normal eyes were studied. Global VAD, VSD, and VCI were reduced in mild POAG vs normal (P<0.02) and moderate-severe vs mild POAG (P<0.04). Stepwise focal reductions across disease stage were demonstrated for OCTA parameters in the inferior hemisphere (P<0.05); reduction in OCTA parameters in mild POAG vs normal was demonstrated in inferior and superior quadrants (P<0.05). Reduced global VF MD was associated with reduced VAD, VSD, and VCI (P=0.0007, 0.0013, <0.0001; R2=0.449, 0.312, 0.399, respectively), and global RNFL thickness was associated with VAD, VSD, and VCI (P<0.0001; R2=0.499, 0.524, 0.542), superior and inferior hemifield MD were associated with corresponding VAD, VSD, and VCI (P≤0.001; R2 from 0.208 to 0.513). RNFL thickness in all quadrants was associated with corresponding OCTA parameters (P<0.05; R2 from 0.213 to 0.394), except temporal VAD and VCI. Area under curves for VAD, VSD, and VCI demonstrated good diagnostic ability (0.868, 0.855, 0.868; P<0.0001). Conclusion: Glaucomatous eyes showed stepwise reductions in RNFL microcirculation across severity; focal reductions in the inferior hemisphere and inferior and superior quadrants were most significant. OCTA parameters had stronger associations with structural rather than functional measures of glaucoma.
关键词： optic nerve head,segmentation,function,large vessel subtraction,diagnostic accuracy,microcirculation,structure
更新于2025-09-09 09:28:46
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[IEEE 2018 15th Workshop on Positioning, Navigation and Communications (WPNC) - Bremen, Germany (2018.10.25-2018.10.26)] 2018 15th Workshop on Positioning, Navigation and Communications (WPNC) - Design and Accuracy Evaluation of a RSS-Based Visible Light Positioning Implementation
摘要： In this work the design of a transmitter and receiver for indoor visible light positioning is elaborated. The dedicated design is then deployed to conduct measurements to obtain the estimated distance between transmitter and receiver. The results show that the error on the distance estimation between transmitter and receiver is below 3 cm for a realistic setting and good overall performance is achieved. Some additional measurements are done near a re?ecting surface to estimate the in?uence of the none-line of sight component on the received optical power.
关键词： RSS-Based,Visible Light Positioning,Indoor Positioning,Visible Light Communication,Accuracy Evaluation
更新于2025-09-09 09:28:46